Abstract: To address the issues of multiple causes, strong coupling, and lack of quantitative basis in decision-making for low-voltage problems in distribution feeders, a quantitative analysis method for low-voltage causes based on three-phase four-wire load flow calculation is proposed. The method constructs a detailed feeder model considering load unbalance, neutral conductor, and grounding loop effects, and calculates the nodal voltage distribution using the forward-backward sweep method. A low-voltage index is introduced as a comprehensive evaluation metric. Through parametric analysis, single-variable perturbation calculations are performed on transformer capacity and tap settings, line conductor sizes, reactive power compensation, and three-phase load unbalance to achieve quantitative assessment and identification of the primary causes of low voltage. Case study results indicate that the proposed method can effectively characterize low-voltage features of the feeder, distinguish the influence degree of different mitigation factors, and provide a quantitative decision-making basis for precise low-voltage control.

Key words: low-voltage governance, power flow calculation, three-phase four-wire system, quantitative analysis, distribution station area simulation